First-principles study of possible shallow donors in ZnAl2O4 spinel

ZnAl2O4 (gahnite) is a ceramic which is considered a possible transparent conducting oxide (TCO) due to its wide band gap and transparency for UV. Defects play an important role in controlling the conductivity of a TCO material along with the dopant, which is the main source of conductivity in an otherwise insulating oxide. A comprehensive first-principles density functional theory study for point defects in ZnAl2O4 spinel is presented using the Heyd, Scuseria, and Ernzerhof hybrid functional (HSE06) to overcome the band gap problem. We have investigated the formation energies of intrinsic defects which include the Zn, Al, and O vacancy and the antisite defects: Zn at the Al site (Zn-Al) and Al at the Zn site (Al-Zn). The antisite defect Al-Zn has the lowest formation energy and acts as a shallow donor, indicating possible n-type conductivity in ZnAl2O4 spinel by Al doping

Pulsed electron beam induced recrystallization and damage in GaAs

Single-pulse electron-beam irradiations of 300-keV 10^(15)Kr+/cm^2 or 300-keV 3×10^(12)Se+/cm^2 implanted layers in unencapsulated GaAs are studied as a function of the electron beam fluence. The electron beam pulse had a mean electron energy of ~-20 keV and a time duration of ~-10^(–7) s. Analyses by means of MeV He + channeling and TEM show the existence of narrow fluence window (0.4–0.7 J/cm^2) within which amorphous layers can be sucessfully recrystallized, presumably in the liquid phase regime. Too high a fluence produces extensive deep damage and loss of As

Smoking as an early risk factor for problematic parenting practices

Parenting among those who use non-illicit and more common drugs such as cigarettes remains an understudied area for investigation. Secondary data analyses were performed in 2015 on a prospective study with parent and twin data available on n=3,009 individual members of female twin pairs born between July 1975 and June 1985 identified from Missouri-state birth records. Maternal smoking when the twins were 3+ years of age remained a significant predictor of offspring report of childhood sexual abuse (OR, 1.40; 95% CI, 1.02-1.92) after controlling for key covariates. Given limited public health resources, mothers who smoke during child's preschool years may be targeted for tailored parenting intervention

Divergent barotropic instability of the tropical asymmetric easterly jet

The divergent barotropic instability of a zonally averaged, observed, tropical, upper tropospheric, monsoon easterly jet is investigated by numerical integration of a linear spectral model. The Rossby radius of deformation for the upper troposphere is computed from a three-layer model of the atmosphere. It is shown that the antisymmetric zonal flow components in the jet contribute in stabilizing the short waves and destabilizing the long waves. Furthermore, the maximum amplitude of the asymmetric preferred wave is shifted southward (to 6°N) to a region where a largest positive maximum of −ūvv is located for the asymmetric profile. A large decrease in the meridional scale of the wave and a threefold increase in the ratio of the computed maximum southward-to-northward easterly momentum transports is also found for the asymmetric jet compared to the symmetric jet. The divergence is found to increase the growth rates of all the waves and, also to increase the preferred wavelength. The most unstable divergent asymmetric wave is shown to have a wavelength of 6500 km, an e-folding time of 6.5 days and a westward phase speed of 23.5 m s−1. The zonal scale of the preferred wave is nearly equal to the Rossby radius of deformation

Steady-state thermally annealed GaAs with room-temperature-implanted Si

Semi-insulating Cr-doped single-crystal GaAs samples were implanted at room temperature with 300-keV Si ions in the dose range of (0.17–2.0)×1015 cm–2 and were subsequently steady-state annealed at 900 and 950°C for 30 min in a H2 ambient with a Si3N4 coating. Differential Hall measurements showed that an upper threshold of about 2×1018/cm3 exists for the free-electron concentration. The as-implanted atomic-Si profile measured by SIMS follows the theoretical prediction, but is altered during annealing. The Cr distribution also changes, and a band of dislocation loops ~2–3 kÅ wide is revealed by cross-sectional TEM at a mean depth of Rp~3 kÅ. Incomplete electrical activation of the Si is shown to be the primary cause for the effect

Lipid Peroxidation Products and Nitric Oxide in the Evaluation of Benign and Malignant Pleural Effusion

Background: Pleural effusion is a common complication of various diseases. Free radicals are known to produce damage in many biological tissues. Free radicals exert their cytotoxic effect by causing lipid peroxidation which is believed to be responsible for the exudation of fluid into the pleural space.Aim: Evaluation of the association of benign and malignant pleural effusion with the free radical induced pleurisy by measurement of lipid peroxidation products and nitric oxide activity.Methods: Case control study was conducted on 50 cases of benign pleural effusion, 50 cases of malignant pleural effusion and 15 cases of healthy controls. Malondialdehyde (MDA) levels were measured by spectrophotometric method with TBA. Nitric Oxide activity was measured by spectrophotometric method using Griess reaction.Results: Our results showed significant increase of MDAs level in both groups of patients: benign and malignant in comparison with control group. Significant increase in the concentrations of nitrate/nitrite depicting total nitric oxide was observed in benign as well as malignant group in comparison to control healthy group.Conclusion: These results suggest that determination of biomarkers of oxidative stress products may be useful in the diagnosis and treatment of patients

Bay of Bengal: From monsoons to mixing

The Bay of Bengal has a surprisingly large influence on the world. It nurtures the South Asian summer monsoon, a tremendous ocean-atmosphere-land phenomenon that delivers freshwater to more than a third of the human population on this planet. During summer, southwesterly winds gather moisture from the ocean and carry it deep inland over the Indian subcontinent, bringing welcome rains to a parched land. During winter, the winds reverse to northeasterly, and the ocean circulation responds by dispersing the terrestrial freshwater run off concentrated in the northern part of the bay

Lipid Peroxidation and Thymidine Phosphorylase expression in Prostate Carcinoma

Aim: To understand the association between markers of oxidative stress and angiogenesis in relation to disease progression, clinical stage and cytological grade in patho-physiology of prostate carcinoma.Patients and Methods: Case control study comprised of 50 prostate carcinoma patients along with 20 age and sex-matched healthy subjects as controls. Levels of malondialdehyde were measured to study the oxidative stress status in the study subjects. Angiogenesis was evaluated by studying the activity of Thymidine Phosphorylase/Platelet derived endothelial cell growth factor.Results: The levels of markers of oxidative stress along with the activity of thymidine phosphorylase were found to be significantly higher in the study subjects in comparison to healthy controls. The results indicate oxidative stress and angiogenesis activity increase progressively with the increase in staging and progression of disease.Conclusion: Oxidative stress and expression of angiogenesis activity points clearly that with the progression of oxidative stress there is a simultaneous progression of angiogenesis in relation to disease progression, clinical stage and cytological grade in the pathophysiology of prostate carcinoma

Effects of magnetic field induced chiral-spin interactions on quasi-one-dimensional spin systems

It is known that in certain non-bipartite quasi-one dimensional spin systems in a magnetic field, in addition to the usual Pauli coupling of the spins to the field, new parity breaking three spin interactions, i.e. chiral spin interactions, are induced at higher order due to virtual processes involving the intrinsic electronic nature of the underlying spins. The strenght of these interactions depend strongly on the orientation of the field, a feature which can be exploited to detect chiral effects experimentally. In many spin systems, these chiral interactions are generated and should be taken into account before any comparison with experiments can be made. We study the effect of the chiral interactions on certain quasi-one-dimensional gapped spin half systems and show that they can potentially alter the physics expected from the Pauli coupling alone. In particular, we demonstrate that these terms alter the universality class of the C-IC transition in spin-tubes. More interestingly, in weakly coupled XX zig-zag ladders, we find that the field induced chiral term can close the singlet gap and drive a second order transition in the non-magnetic singlet sector, which manifests itself as a two component Luttinger liquid-like behaviour in the spin correlation functions. Finally, we discuss the relevance of our results to experiments.Comment: RevTex, 11 pages, 3 figure